From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935960AbdEVVPC (ORCPT ); Mon, 22 May 2017 17:15:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60860 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933776AbdEVVO7 (ORCPT ); Mon, 22 May 2017 17:14:59 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 44FA537E66 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jglisse@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 44FA537E66 Date: Mon, 22 May 2017 17:14:56 -0400 From: Jerome Glisse To: Dan Williams Cc: Andrew Morton , "linux-kernel@vger.kernel.org" , Linux MM , John Hubbard , David Nellans , "Kirill A . Shutemov" , Ross Zwisler Subject: Re: [HMM 08/15] mm/ZONE_DEVICE: special case put_page() for device private pages Message-ID: <20170522211456.GB8168@redhat.com> References: <20170522165206.6284-1-jglisse@redhat.com> <20170522165206.6284-9-jglisse@redhat.com> <20170522201416.GA8168@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.7.1 (2016-10-04) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 22 May 2017 21:14:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 22, 2017 at 01:19:29PM -0700, Dan Williams wrote: > On Mon, May 22, 2017 at 1:14 PM, Jerome Glisse wrote: > > On Mon, May 22, 2017 at 12:29:53PM -0700, Dan Williams wrote: > >> On Mon, May 22, 2017 at 9:51 AM, Jérôme Glisse wrote: > >> > A ZONE_DEVICE page that reach a refcount of 1 is free ie no longer > >> > have any user. For device private pages this is important to catch > >> > and thus we need to special case put_page() for this. > >> > > >> > Signed-off-by: Jérôme Glisse > >> > Cc: Kirill A. Shutemov > >> > Cc: Dan Williams > >> > Cc: Ross Zwisler > >> > --- > >> > include/linux/mm.h | 30 ++++++++++++++++++++++++++++++ > >> > kernel/memremap.c | 1 - > >> > 2 files changed, 30 insertions(+), 1 deletion(-) > >> > > >> > diff --git a/include/linux/mm.h b/include/linux/mm.h > >> > index a825dab..11f7bac 100644 > >> > --- a/include/linux/mm.h > >> > +++ b/include/linux/mm.h > >> > @@ -23,6 +23,7 @@ > >> > #include > >> > #include > >> > #include > >> > +#include > >> > > >> > struct mempolicy; > >> > struct anon_vma; > >> > @@ -795,6 +796,20 @@ static inline bool is_device_private_page(const struct page *page) > >> > return ((page_zonenum(page) == ZONE_DEVICE) && > >> > (page->pgmap->type == MEMORY_DEVICE_PRIVATE)); > >> > } > >> > + > >> > +static inline void put_zone_device_private_page(struct page *page) > >> > +{ > >> > + int count = page_ref_dec_return(page); > >> > + > >> > + /* > >> > + * If refcount is 1 then page is freed and refcount is stable as nobody > >> > + * holds a reference on the page. > >> > + */ > >> > + if (count == 1) > >> > + page->pgmap->page_free(page, page->pgmap->data); > >> > + else if (!count) > >> > + __put_page(page); > >> > +} > >> > #else > >> > static inline bool is_zone_device_page(const struct page *page) > >> > { > >> > @@ -805,6 +820,10 @@ static inline bool is_device_private_page(const struct page *page) > >> > { > >> > return false; > >> > } > >> > + > >> > +static inline void put_zone_device_private_page(struct page *page) > >> > +{ > >> > +} > >> > #endif > >> > > >> > static inline void get_page(struct page *page) > >> > @@ -822,6 +841,17 @@ static inline void put_page(struct page *page) > >> > { > >> > page = compound_head(page); > >> > > >> > + /* > >> > + * For private device pages we need to catch refcount transition from > >> > + * 2 to 1, when refcount reach one it means the private device page is > >> > + * free and we need to inform the device driver through callback. See > >> > + * include/linux/memremap.h and HMM for details. > >> > + */ > >> > + if (unlikely(is_device_private_page(page))) { > >> > >> Since I presume HMM is a niche use case can we make this a > >> "static_branch_unlikely(&hmm_key) && is_device_private_page(page))"? > >> That way non-hmm platforms see minimal overhead. > > > > Like i said in the cover letter i am bit anxious about doing for > > I don't think you copied me on the cover letter. > > > an inline function. I don't see any existing case for inline > > function and static key. Is that suppose to work ? > > > > How widespread HMM use will be is hard to guess. Usual chicken > > and egg plus adoption thing. If GPGPU compte keeps growing and > > it seems it does then HMM likely gonna be enable and actively > > use for large chunk of those computer that have GPGPU workload. > > > > I will test a static key of that branch and see if it explodes > > because put_page() is an inline function. > > memcpy_mcsafe() is an existing example of a static inline with a > static branch. Hasn't seemed to have caused any problems to date. Ok i will post a new version of 08 with static keys, i shouldn't need to repost any other patches for that. Andrew that's fine with you or do you prefer me to repost a full updated patchset ? Cheers, Jérôme From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id 31E366B02B4 for ; Mon, 22 May 2017 17:15:01 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id o85so57915784qkh.15 for ; Mon, 22 May 2017 14:15:01 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id y68si10560856qkc.250.2017.05.22.14.15.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 May 2017 14:15:00 -0700 (PDT) Date: Mon, 22 May 2017 17:14:56 -0400 From: Jerome Glisse Subject: Re: [HMM 08/15] mm/ZONE_DEVICE: special case put_page() for device private pages Message-ID: <20170522211456.GB8168@redhat.com> References: <20170522165206.6284-1-jglisse@redhat.com> <20170522165206.6284-9-jglisse@redhat.com> <20170522201416.GA8168@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Andrew Morton , "linux-kernel@vger.kernel.org" , Linux MM , John Hubbard , David Nellans , "Kirill A . Shutemov" , Ross Zwisler On Mon, May 22, 2017 at 01:19:29PM -0700, Dan Williams wrote: > On Mon, May 22, 2017 at 1:14 PM, Jerome Glisse wrote: > > On Mon, May 22, 2017 at 12:29:53PM -0700, Dan Williams wrote: > >> On Mon, May 22, 2017 at 9:51 AM, Jerome Glisse wrote: > >> > A ZONE_DEVICE page that reach a refcount of 1 is free ie no longer > >> > have any user. For device private pages this is important to catch > >> > and thus we need to special case put_page() for this. > >> > > >> > Signed-off-by: Jerome Glisse > >> > Cc: Kirill A. Shutemov > >> > Cc: Dan Williams > >> > Cc: Ross Zwisler > >> > --- > >> > include/linux/mm.h | 30 ++++++++++++++++++++++++++++++ > >> > kernel/memremap.c | 1 - > >> > 2 files changed, 30 insertions(+), 1 deletion(-) > >> > > >> > diff --git a/include/linux/mm.h b/include/linux/mm.h > >> > index a825dab..11f7bac 100644 > >> > --- a/include/linux/mm.h > >> > +++ b/include/linux/mm.h > >> > @@ -23,6 +23,7 @@ > >> > #include > >> > #include > >> > #include > >> > +#include > >> > > >> > struct mempolicy; > >> > struct anon_vma; > >> > @@ -795,6 +796,20 @@ static inline bool is_device_private_page(const struct page *page) > >> > return ((page_zonenum(page) == ZONE_DEVICE) && > >> > (page->pgmap->type == MEMORY_DEVICE_PRIVATE)); > >> > } > >> > + > >> > +static inline void put_zone_device_private_page(struct page *page) > >> > +{ > >> > + int count = page_ref_dec_return(page); > >> > + > >> > + /* > >> > + * If refcount is 1 then page is freed and refcount is stable as nobody > >> > + * holds a reference on the page. > >> > + */ > >> > + if (count == 1) > >> > + page->pgmap->page_free(page, page->pgmap->data); > >> > + else if (!count) > >> > + __put_page(page); > >> > +} > >> > #else > >> > static inline bool is_zone_device_page(const struct page *page) > >> > { > >> > @@ -805,6 +820,10 @@ static inline bool is_device_private_page(const struct page *page) > >> > { > >> > return false; > >> > } > >> > + > >> > +static inline void put_zone_device_private_page(struct page *page) > >> > +{ > >> > +} > >> > #endif > >> > > >> > static inline void get_page(struct page *page) > >> > @@ -822,6 +841,17 @@ static inline void put_page(struct page *page) > >> > { > >> > page = compound_head(page); > >> > > >> > + /* > >> > + * For private device pages we need to catch refcount transition from > >> > + * 2 to 1, when refcount reach one it means the private device page is > >> > + * free and we need to inform the device driver through callback. See > >> > + * include/linux/memremap.h and HMM for details. > >> > + */ > >> > + if (unlikely(is_device_private_page(page))) { > >> > >> Since I presume HMM is a niche use case can we make this a > >> "static_branch_unlikely(&hmm_key) && is_device_private_page(page))"? > >> That way non-hmm platforms see minimal overhead. > > > > Like i said in the cover letter i am bit anxious about doing for > > I don't think you copied me on the cover letter. > > > an inline function. I don't see any existing case for inline > > function and static key. Is that suppose to work ? > > > > How widespread HMM use will be is hard to guess. Usual chicken > > and egg plus adoption thing. If GPGPU compte keeps growing and > > it seems it does then HMM likely gonna be enable and actively > > use for large chunk of those computer that have GPGPU workload. > > > > I will test a static key of that branch and see if it explodes > > because put_page() is an inline function. > > memcpy_mcsafe() is an existing example of a static inline with a > static branch. Hasn't seemed to have caused any problems to date. Ok i will post a new version of 08 with static keys, i shouldn't need to repost any other patches for that. Andrew that's fine with you or do you prefer me to repost a full updated patchset ? Cheers, Jerome -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org